The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device and, particularly, to a semiconductor device having insulating films of a multilayer structure on a fuse wire and a method of manufacturing the semiconductor device.
As a technology of repairing a failure occurring in a circuit such as a DRAM or SRAM by a redundancy circuit, a technology of using a part of a metal wire as a fuse wire is known. In this case, a laser beam is used to cut the fuse wire and remove an insulating film above the fuse wire. To properly perform both of the cutting and removing, conditions (wavelength, output time, and the like) of a laser beam have to be set properly.
However, even when conditions of a laser beam are set properly, it is difficult to properly perform both of the cutting and removing due to dispersions in the thickness of the insulating film above the fuse wire.
To solve the problem, a method of reducing the influence on the cutting and removing of the dispersions in the thickness of the insulating film above the fuse wire can be considered.
However, in the case where the insulating film above the fuse wire is too thin, a problem arises such that a crack occurring in a device verification test extends from an aluminum (Al) pad wire to a wire just below the pad wire. The test is conducted by making a needle of a tester come into contact with a terminal via on a pad wire (a test for verifying electrical operation of the semiconductor device).
In hot and humid environments, there is a problem such that the wiring material just below the pad wire corrodes due to moisture entering from the crack.
Therefore, although the pad wire and the insulating film of the wire just below the pad wire are desirably thick, it is simultaneously necessary to reduce the influence on the laser beam by reducing dispersions in the film thickness.
There is another known technology. As shown in FIG. 7 of Japanese Patent Application Laid-open Publication No. 2001-274247, a thick insulating film (an Si oxide 13, an SOG film 14, and an Si oxide 15) of a multilayer structure made of two or more materials is formed on a fuse wire 12a. By controlling etching time, the etching is stopped in the surface of the silicon oxide 13. In such a manner, the insulating film on the fuse wire 12a is thinned.
However, generally, the thicker the film is, the more etching dispersions. In the case where the dispersions occur in the etching of the SOG film 14, a part of the SOG film 14 remains on the surface of the silicon oxide 13. As a result, dispersions occur in the film thickness above the fuse wire 12a.
Since the energy absorption amount of the laser beam of the SOG film 14 remained is different from that of the silicon oxide 13, it is difficult to properly cut the fuse wire 12a.
The remained SOG film 14 causes a crack in the Si oxide 11 by a shock of blowing off the insulating film (the Si oxide 11 and the silicon oxide 13) around the fuse wire 12a at the time of cutting the fuse wire 12a.
Consequently, in the conventional technology and Japanese Patent Application Laid-open Publication No. 2001-274247, the thick insulating film above the fuse wire cannot be uniformly thinned by etching.